Strange code in WndProc()

[John E]

My memory of Petzold style programming is a bit hazy but while trying to locate a bug (in a 3rd party's code) I came across this:-

LRESULT CALLBACK
WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message) {

		// Some other stuff

	case WM_MOUSEWHEEL:
	case WM_MOUSEHWHEEL:
		PostMessage(hwnd, message, wParam, lParam);
		return 0;
	default:
			// calls DefWindowProc() as usual
	}
}

The parameters used for PostMessage() are the same parameters received by WndProc() (unchanged). Wouldn't that result in an endless loop whenever WM_MOUSEWHEEL or WM_MOUSEHWHEEL gets received The effect is just to re-send the message isn't it? (as I said, my memory's a bit hazy on this stuff !!)